[gentoo-portage-dev] [PATCH] dep_zapdeps: install new package, avoid downgrade (bug 635540)

[Zac Medico]

Prefer to install a new package rather than to downgrade an
installed package. If the installed package should be
downgraded due to it being masked, then allow the downgrade.

Bug: https://bugs.gentoo.org/635540
---
 pym/portage/dep/dep_check.py                       | 11 ++-
 .../tests/resolver/test_or_downgrade_installed.py  | 97 ++++++++++++++++++++++
 2 files changed, 107 insertions(+), 1 deletion(-)
 create mode 100644 pym/portage/tests/resolver/test_or_downgrade_installed.py

diff --git a/pym/portage/dep/dep_check.py b/pym/portage/dep/dep_check.py
index 35caecc74..2c69c1c48 100644
--- a/pym/portage/dep/dep_check.py
+++ b/pym/portage/dep/dep_check.py
@@ -323,8 +323,10 @@ def dep_zapdeps(unreduced, reduced, myroot, use_binaries=0, trees=None):
 	want_update_pkg = trees[myroot].get("want_update_pkg")
 	downgrade_probe = trees[myroot].get("downgrade_probe")
 	vardb = None
+	vardb_match_pkgs = None
 	if "vartree" in trees[myroot]:
 		vardb = trees[myroot]["vartree"].dbapi
+		vardb_match_pkgs = getattr(vardb, 'match_pkgs', None)
 	if use_binaries:
 		mydbapi = trees[myroot]["bintree"].dbapi
 	else:
@@ -355,6 +357,7 @@ def dep_zapdeps(unreduced, reduced, myroot, use_binaries=0, trees=None):
 		all_use_satisfied = True
 		all_use_unmasked = True
 		conflict_downgrade = False
+		installed_downgrade = False
 		slot_atoms = collections.defaultdict(list)
 		slot_map = {}
 		cp_map = {}
@@ -419,6 +422,12 @@ def dep_zapdeps(unreduced, reduced, myroot, use_binaries=0, trees=None):
 						avail_pkg = avail_pkg_use
 					avail_slot = Atom("%s:%s" % (atom.cp, avail_pkg.slot))
 
+			if vardb_match_pkgs is not None:
+				inst_pkg = vardb_match_pkgs(avail_slot)
+				if (inst_pkg and avail_pkg < inst_pkg[-1] and
+					not downgrade_probe(inst_pkg[-1])):
+					installed_downgrade = True
+
 			slot_map[avail_slot] = avail_pkg
 			slot_atoms[avail_slot].append(atom)
 			highest_cpv = cp_map.get(avail_pkg.cp)
@@ -487,7 +496,7 @@ def dep_zapdeps(unreduced, reduced, myroot, use_binaries=0, trees=None):
 						unsat_use_installed.append(this_choice)
 					else:
 						unsat_use_non_installed.append(this_choice)
-			elif conflict_downgrade:
+			elif conflict_downgrade or installed_downgrade:
 				other.append(this_choice)
 			else:
 				all_in_graph = True
diff --git a/pym/portage/tests/resolver/test_or_downgrade_installed.py b/pym/portage/tests/resolver/test_or_downgrade_installed.py
new file mode 100644
index 000000000..22307a5bc
--- /dev/null
+++ b/pym/portage/tests/resolver/test_or_downgrade_installed.py
@@ -0,0 +1,97 @@
+# Copyright 2017 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+
+from portage.tests import TestCase
+from portage.tests.resolver.ResolverPlayground import (
+	ResolverPlayground,
+	ResolverPlaygroundTestCase,
+)
+
+class OrDowngradeInstalledTestCase(TestCase):
+
+	def testOrDowngradeInstalled(self):
+		ebuilds = {
+			'net-misc/foo-1': {
+				'EAPI': '6',
+				'RDEPEND': '|| ( sys-libs/glibc[rpc(-)]  net-libs/libtirpc )'
+			},
+			'net-libs/libtirpc-1': {
+				'EAPI': '6',
+			},
+			'sys-libs/glibc-2.26': {
+				'EAPI': '6',
+				'IUSE': ''
+			},
+			'sys-libs/glibc-2.24': {
+				'EAPI': '6',
+				'IUSE': '+rpc'
+			},
+		}
+
+		installed = {
+			'sys-libs/glibc-2.26': {
+				'EAPI': '6',
+				'IUSE': ''
+			},
+		}
+
+		world = ['sys-libs/glibc']
+
+		test_cases = (
+			# Test bug 635540, where we need to install libtirpc
+			# rather than downgrade glibc.
+			ResolverPlaygroundTestCase(
+				['net-misc/foo'],
+				success=True,
+				mergelist=[
+					'net-libs/libtirpc-1',
+					'net-misc/foo-1',
+				],
+			),
+		)
+
+		playground = ResolverPlayground(debug=False,
+			ebuilds=ebuilds, installed=installed, world=world)
+
+		try:
+			for test_case in test_cases:
+				playground.run_TestCase(test_case)
+				self.assertEqual(test_case.test_success, True,
+					test_case.fail_msg)
+		finally:
+			playground.debug = False
+			playground.cleanup()
+
+		# In some cases it's necessary to downgrade due to
+		# the installed package being masked (glibc is a
+		# not an ideal example because it's usually not
+		# practical to downgrade it).
+		user_config = {
+			"package.mask" : (
+				">=sys-libs/glibc-2.26",
+			),
+		}
+
+		test_cases = (
+			ResolverPlaygroundTestCase(
+				['net-misc/foo'],
+				success=True,
+				mergelist=[
+					'sys-libs/glibc-2.24',
+					'net-misc/foo-1',
+				],
+			),
+		)
+
+		playground = ResolverPlayground(debug=False,
+			ebuilds=ebuilds, installed=installed, world=world,
+			user_config=user_config)
+
+		try:
+			for test_case in test_cases:
+				playground.run_TestCase(test_case)
+				self.assertEqual(test_case.test_success, True,
+					test_case.fail_msg)
+		finally:
+			playground.debug = False
+			playground.cleanup()
-- 
2.13.5